flashback transaction query可以从FLASHBACK_TRANSACTION_QUERY中获得指定事务的历史信息以及Undo_SQL
通过这个UNDO_SQL，查询具体事务所做的操作、我们就可以恢复特定的事务、flashback transaction query测试
OCP考题：
13. You executed the following query:
SELECT operation, undo_sql, table_name FROM flashback_transaction_query;
Which statement is correct regarding the query output?
A. It would return information regarding only the last committed transaction.
B. It would return only the active transactions in all the undosegments in the database.
C. It would return only the committed transactions in all the undo segments in the database.
D. It would return both active and committed transactions in all the undo segments in the database.
E. It would return information regarding the transactions that began and were committed in the last 30 minutes.
Answer: D